Parathormone induces

$A$ deficiency of which of the following leads to a decrease in blood calcium levels?

Tetany $(Irregular \text{ muscle contraction})$ and osteoporosis are caused due to the deficiency of

Which of the following are not the effects of Parathyroid hormone $(PTH)$?
$(a)$ Stimulates the process of bone resorption
$(b)$ Decreases $Ca^{2+}$ level in blood
$(c)$ Reabsorption of $Ca^{2+}$ by renal tubules
$(d)$ Decreases the absorption of $Ca^{2+}$ from digested food
$(e)$ Increases metabolism of carbohydrates
Choose the most appropriate answer from the options given below:

Increase in the excitability of nerves and muscles leading to sustained contraction of the muscles of larynx,face,hand and feet is due to

Which of the following hormone levels,when decreased,leads to tetany?